xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan) (07/13/90)
In article <1126@kirk.nmg.bu.oz> cameron@kirk.nmg.bu.oz (Cameron Stevenson) writes: >From article <1990Jun28.143847.9013@gpu.utcs.utoronto.ca>, by tj@gpu.utcs.utoronto.ca (Terry Jones): >> DXF files are object oriented. Group 3 FAX and PBM are bitmap formats. > >I think it incorrect to call DXF files object-oriented. Autodesk has been >using this term for a while now to distinguish AutoCAD from painting >applications. What they SHOULD be calling AutoCAD (and what you should >therefore be calling DXF files) is vector based. As you have correctly >stated, FAX, GIF, and heaps more are bitmap (or pixel) file format - ie. >this dot is black, the next one is white, and so on... > >Vector based file formats store the definition of a line (or any other >graphical element) - ie. this line starts here, is so thick, and goes there, >and so on... > >Object-oriented files (or more correctly, the data created by object-oriented >systems) store both the data (ala pixel and vector files) AND some code >within the object - ie. I am a line, and when I receive a message to display >myself, I will start here, and end here, but if I recieve a message to >tell how long I am I will return a number, and so on... > > >Sorry to be picky, but it annoys me when Autodesk call AutoCAD an >object-oriented CAD package. It is true, there are some object-oriented >CAD packages around (most in experimental stages), but AutoCAD is NOT >one of them. The implication from Autodesk (I think!) is that AutoCAD >has something that it's competitors doesn't, and most CAD purchasers >don't know enough about the subject to question them. A sense of history helps here; your complaint is quite unfair. The usage of "object oriented" has existed for computer graphics since long before it became a buzzword for computer languages, and has nothing to do with packing code within the object. It is used to distinguish those systems in which the things displayed exist as structured objects, such that one may be moved, deleted, or recolored (for example) and the picture redrawn correctly (usually from a display list), from those where the things displayed exist as pixels (for raster systems) or lines (for calligraphic) systems, and have no higher structure, and therefore these low level entities, rather than the orginal objects, are all that can be manipulated to modify the display. Kent, the man from xanth. <xanthian@Zorch.SF-Bay.ORG> <xanthian@well.sf.ca.us> -- Kent, I agree with you 1000%!!!!!!!!!! -- John J. Wood